160 SPOKOZOA. 



Drepanidium princeps, Labbe, 1894, p. 76. 



Lankesterella ranarum, Labbe, 1899, p. 74 ; Minchin, 1903, pp. 239, 



253-7, 260, 261, 265, 267, 270, 345 ; 1912, pp. 372-8. 

 Lankesterella minima Minchin 1903 p. 265. 

 '\ Lankesterella minima, Patton, 1908, p. 319 ; 1909, pp. 146-7. 

 Hsemogregarina minima Mathis & Leger, 1911, pp. 448-9. 

 Lankesterella minima, Minchin, 1912, p. 372 ; Noller, 1912, pp. 201-8, 



pi. xx; 1913 a, pp. 313-16; 1913 6, pp. 222-32, pi. xiv, figs. 55- 



68 ; pi. XV, figs. 69-72 ; 1920 a, pp. 169-89, pis. iv-vi; Wenyon, 



1926, pp. 878-80, fig. 380 ; p. 1105. 

 ■\ Lankesterella minima, Scott, 1926, pp. 237-8 ; 1927, pp. 190-1. 

 Lankesterella minima, Reichenow, 1929, pp. 964-5, fig. 930 ; Kudo, 



1931, p. 276, fig. 15, g. 

 Lankesterella ranarum. Calkins, 1933, p. 545, fig. 218, B, C. 



Infection of the frog is brought about by a leech, which 

 introduces the sporozoites. Sporozoites make their way into 

 the blood- capillaries of various organs, and apparently enter 

 the endothehal cells, where the entire development takes place. 

 Each sporozoite becomes rounded, grows into a schizont, 

 and produces a large number of merozoites. The merozoites 

 escape into the blood and infect other endothehal cells. Mero- 

 zoites of a special kind are finally produced, and these, after 

 entering the endothehal cells, develop into micro- and macro - 

 gametocytes. Microgametocyte produces a large number of 

 microgametes, and fertilization of the macrogamete results. 

 An oocyst is formed round the zygote, which breaks up directly, 

 without the formation of sporoblasts and sporocysts, into 

 a number of sporozoites. The latter, by rupture of the oocyst, 

 escape into the blood and enter red blood-corpuscles. Here 

 the sporozoite is seen as a small vermicule, which may attain 

 half the length, but no more, of the corpuscle. The leech 

 sucks up sporozoites with the blood and transfers them 

 mechanically to another frog (tadpole). 



Dimensions. — Sporozoite 10-15 /a in length. 



Remarks. — ^The cycle as described above is based on the 

 researches of Noller (1912, 1913, 1920). As Wenyon has 

 remarked : " if this cycle of development is confirmed, it is 

 a remarkable one in that the whole development, up to the 

 formation of sporozoites, takes place in the endothehal ceUs 

 of the blood-vessels, and is an illustration of a coccidium, 

 originally transferred from host to host in the oocyst stage, 

 as in the more typical forms, having become adapted to hfe 

 in the blood-stream. . . . The possibihty of the escape of the 

 oocysts to the exterior having been lost by this change of 

 habit, the difficulty is overcome by the leech transferring 

 from host to host." 



Some observers have described the vermicule as becoming 

 spherical and undergoing schizogony in the red blood-corpuscles, 



